Fri Oct 6 12:32:48 EDT 1995

OK, I got a copy of but it appears corrupted. Can anyone point me
to a good source for the code ???  (contest)!!!!
*  W8CAR pems_st_dk at                                 * 
*  Dan Kovatch                                                     *
*  Antennas are the key - BUT an ALPHA sure doesn't hurt!          *

>From Larry Schimelpfenig <lschim at>  Fri Oct  6 17:51:39 1995
From: Larry Schimelpfenig <lschim at> (Larry Schimelpfenig)
Date: Fri, 6 Oct 1995 12:51:39 -0400 (EDT)
Subject: Slopers Fred Hopengarten
Message-ID: <Pine.SUN.3.91.951006123213.21674A-100000 at>

Bill, it's sad to note the losses that Steve suffered, while happy that 
you and RJ lucked out.

In my travels around the country with the Coast Guard I have made 
extensive use of slopers. Typically I used the top three guy wires on a 
60 or 70 foot tower as slopers on 80. The tower usually had a two element 
triband quad on top. The system played very well.

When I was running the MARS station here in Alexandria (K4CG) circa 78-82 I 
had a quarter wave sloper on a 60 foot self supporting wind mill type tower 
with a KT34XA at the top. This site used to be a Coast Guard 
Communication Station, and still has ground screens running all over the 
place. One is under this tower, and the sloper was a killer. Howie K4PQL 
and I tried all sorts of configurations of wire supported by 100 to 120 
foot towers to improve on the performance of that sloper. It was a waste 
of time! 

I also put a quarter wave sloper off the top of a 120 footer that 
supported a 4 element Telrex 20 meter monobander. It also played 
exceptionally well.

The only time I couldn't get a sloper to play was at my present qth. 
After getting 55ft of tower with 8 feet of mast sticking out the top in 
the air, I decided to put an 80 meter quarter slope up. Didn't matter how 
much wire I used, it wouldn't resonate. As soon as I stuck the KT34XA at 
the 55ft level and cut the sloper to a quarter wave it resonated. Or 
maybe I would be safer to say the vswr in the cw part of the band dropped 
to below 1.5:1! Putting the rotatable 40 meter dipole at the top of the 
mast made no difference in the vswr curve on 80. 

At my present qth, my gut feeling is that the N4KG reverse fed ground 
plane outplays the sloper, but I can't make an a/b comparison because of 
the interaction between the two when they are both on the tower. 

I've seen a number of folks say they couldn't get a sloper to work. I've 
had 8 slopers or sloper systems up at various locations and the only one 
that didn't work didn't have a top hat.

de Larry K7SV - lschim at

>From David O. Hachadorian" <74752.115 at  Fri Oct  6 17:48:46 1995
From: David O. Hachadorian" <74752.115 at (David O. Hachadorian)
Date: 06 Oct 95 12:48:46 EDT
Subject: K6LL/6
Message-ID: <951006164846_74752.115_EHL125-1 at CompuServe.COM>

If you hear K6LL on Saturday, it will be from Imperial County,
CA, NOT Arizona. We will be screwing around with an all-band
vertical over salt water (Salton Sea,) just to see how it works,
and to pass out a few CQP Q's until sundown.

Dave, K6LL
74752.115 at

>From jreid at (Jim Reid)  Fri Oct  6 18:20:50 1995
From: jreid at (Jim Reid) (Jim Reid)
Date: Fri, 06 Oct 1995 07:20:50 -1000
Subject: Insurance
Message-ID: <199510061720.HAA01320 at>

Aloha from Kauai, Bill,

Hope you don't have the same experience with insurance
companies as we have our here since Iniki wiped us out
three years ago.  No insurance company  will sell any
hurricane/wave wash coverage in Hawaii.  The State of
Hawaii has established a "pool".  Any  home owner can
participate,  as long as he has a "regular"  home owners
policy;  which of course,  no mainland insurance company
will now sell on Kauai!  So now, the only homeowners policies
available are from State of Hawaii insurance companies,
one of whom  could not pay out all the damages for which
they were liable (if that is the correct term in the insurance
business when a policy holder has a loss.)  So  many,
many insured homes on Kauai were repaired by loans
from FEMA,  the SBA,  etc.,  as the insurance companies
had not enough money to cover the damages!

Same thing with our automobiles.  Mainland companies,
most of them anyway,  have backed out.  I  am now
covered by Daiwa Insurance Co.  Guess where
they are located!

Seems too bad the American mainland insurance companies
wish to pretend that Hawaii is a foreign country,  as does the
DXCC.  We feel just a bit abandoned.  Maybe I should throw
my support to the Hawaiian Sovereignty Movement (not
sure I spelled thay right).

You cannot get insurance on antennas or towers even if
they are a structural part of your home out here!

73 and best of good fortune as you clean up and repair.

Jim,  AH6NB

>From broz at (John Brosnahan)  Fri Oct  6 18:48:34 1995
From: broz at (John Brosnahan) (John Brosnahan)
Date: Fri, 6 Oct 1995 11:48:34 -0600
Subject: 91B info in response to W0UN
Message-ID: <199510061748.LAA16901 at>

After I suggested that the 91B discussion be taken off line to save
reflector BW, I received 8 or 10 requests from interested parties that it be
kept on line.  In the mean time Garry responded directly to me and with the
outpouring of interest I suggested that he cc: the reflector with his latest
comments, but unfortunately he isn't able to and asked me to repost his
message as well as my final comments, in order to satisfy the cravings for
91B info.

--John  W0UN

(from NI6T)

Many thanks for your detailed response, to which I add only a few 

You wrote: 

>The demands placed on a generator by a rapidly varying current load 
from a
>keyed or ssb modulated amplifier are especially difficult for a 
>since the time constant of the varying load is much faster than the 
>constant of the response time of the mechanical governors on 
>This can be helped by running oversize generators (where the mass of 
>generator itself provides an additional flywheel effect) but this is
>difficult on an expedition. 

Virtually impossible, in fact. The decision to purchase the 3kVA Robin 
Diesel was made after many FAX exchanges between Mats and myself. I had 
done rough calculations as to what the amp might require or 
--alternatively--what we could expect from it for a given generator 
capapcity. Naturally, cost and weight were issues. Mats was justifiably 
concerned about moving generators across the reef. The Robin was a 
beautiful unit, however, with a self-starter, and ran like a clock. 
Diesel fuel is safer, of course, and there did not seem to be much of a 
weight penalty: it was about the same size as the 3.3 kVA gasoline 
unit. The battery for the self-starter became the means for putting a 
third station on the air, after losing a crucial power supply 
overboard. Mats spliced two battery cables, connecting his IC735 to the 
raw DC output of the Robin; the battery provided the peak current 
needed and he was QRV.

> It is also important to minimize the percentage
>change from min load to max load by running as much on the generator 
>possible so that max load is near the capacity of the generator by 
>lights and other gear even during the daytime to increase the current 
>under "min load"--ie amp not keyed.  This reduces the range over which 
>governor needs to to work and makes sure that the generator is not 
>during receive periods. 

With only a 3kVA generator, adding more loads only served to deprive 
the amp of steady-state power. In a situation like that, you are damned 
either way. 

>I was momentarily confused by "emitter" resistors in a vacuum tube amp 
but I
>assume that transistor terminology has become pervasive and that you 
>the cathode resistors...

Har! Yes, that is exactly right. After 30 years of solid state 
electronics, I have forgotten what a cathode is.

 But the progressive failure of the cathode resistors
>doesn't explain the time delay that you noted between amp switching 
and the
>appearance of power.

Maybe not, but the time delay did increase, so perhaps the increase in 
cathode resistance influenced the control circuitry.

>Unbypassed cathode resistors do provide negative feedback (ie 
>and result in more drive being required but in a grid driven amp with 
>of drive this is not a bug but a feature since you are throwing away 
most of
>your drive power in the untuned grid resistor anyway. 

I did not say it was a bug, and I am sure degeneration is used 
precisely to prevent overdrive by lowering gain.

  Any change in plate
>efficiency one way or the other is so small as to be a 
wash--especially in
>view of the requirement to add some series resistance in the plate 
lead to
>limit the energy dissipated inside the tube during an arc over.  
>this plate resitor will be on the order of 50 ohms and a cathode bias
>resistor will be about 1/5 of this value.  With only a few watts 
>required in the cathode resistor this is pretty insignificant compared 
>the 2 kilowatts of anode input power. 

Good point.

>But I must disagree with you on the statement of slightly compromised 
>statement when using catode resistors. (Snip)

 The Eimac
>design uses 11 ohms for the 4CX600J and the ETO 91B uses 12 ohms for 
>Svetlana 4CX800, which is a pretty close match to Eimac's design.

Actually, one always would expect degenerative feedback to reduce 
distortion, but I was actually looking at the published numbers in the 
Svetlana 4CX1600B data sheet--using 24 ohms and an apparently large 
conduction angle. I do understand that IMD numbers are misleading, due 
to to sensitivity of the cusps to operating point.I learned long 
ago--in an undergrad electronics lab project--that 
amplifiers--especially tetrode amplifiers---have so many interactive 
parameters as to make such comparisons quite difficult. My "test amp" 
then was my own homebrew pair of 6146's.

>I have to admit that I am a homebrew fan as well and I am building a 
>of single band 8877 amps.  I chose the 8877 since I had a lot of pulls 
>over from atmospheric radar projects.  If I were to go out and buy new 
>I would choose the Svetlana tubes at this point due to their price
>differential.  I feel that they are good tubes at a bargain price.  
>tubes in general are also good tubes but are becomming prohibitively
>expensive for ham use, unfortunately.
That price differential is providing a feast for George Badger, W6TC, 
and Svetlana. The 4CX800A is priced virtually at the Eimac 3-500Z and 
the retail price for a 4CX1600B is only about $385! And I am told these 
prices are much more than what they can be had for in Russia! Ehrhorn 
is no fool: he has really created some gross margin by dropping his 
manufacturing and parts costs!

DXpeditioning, contesting, my newsletter and DXing have kept me from 
diving into this amp, and I do not have your resources, but I have 
accumulated most of the parts, and am eagerly anticipating the joy of 
building the beast--something I wanted to do as a kid. The local flea 
markets have been productive.  Wish I had a sheet-metal shop, but I do 
have access to help. I could use a 50 ohm 100W globar--the resistors I 
have are larger. Got any kicking around?

>I will try to work closely with the Heard group to insure reliable 
>of the 91Bs.  My support is available both before the expedition and 
>it.  I feel pretty knowledgeable about the amps but obviously not as
>knowledgeable as the designers at ETO.

I am glad that you are there as a resource for the Heard Herd.One feels 
pretty helpless when the amp craps out in the middle of nowhere. I do 
feel, however, that for most DXpeditions, it probably makes sense to 
bring a moderate-size amp. 500W is a great improvement over 100 watts, 
and such an amp is certainly more manageable in terms of carrying, 
shipping and powering. That was the lesson I took home for next time.
Garry, NI6T

response of W0UN

Garry, after my comment about the lengthy discussion and taking it off-line
from the reflector, I received a number of comments about how our discussion
was one of the more infomative ones in recent months and please don't take
it off the reflector.  Since I think we have wound down a bit at this point
and since I think your most recent comments were sent directly to me you may
way to cc: the reflector just to bring this to a close with all of the lurkers.

Been an enjoyable discussion and you raised a number of interesting
technical issues that got the juices flowing and got the old books down from
the shelf.  The cathode bias resistor is more complex in its effect than I
had recalled but it was nice to review all of my old books (and not find
much, in fact only one reference) and then give Eimac a call.  Been a while
since I have talked to the factory.  

I will continue to try and help ETO with the Alpha 91B issues and at a loss
to figure out what is involved with the delayed output issue.  WIll check
the schematics in more detail for some clue.

73 and thanks for the interesting discussion.

John  W0UN

BTW  if you cc: your latest note to the reflector then I will cc: this one
so that the lurkers know that it has quieted down with amicable results.  HI

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